Traffic control lamps and warning lamps need to emit light in an omni-direction in order to properly signal those approaching the lamps from all directions. Traffic control and warning lamps are generally used on land at road construction and building construction sights. Similar lamps are useful in water applications to signal and warn approaching watercraft of docks, jetties, and obstacles. These lamps emit either a continuous light or a blinking light.
Incandescent light bulbs which comprise filaments are well known to be useful for emitting omni-directional light, wherein light is emitted in 360 degrees about the bulb. See for example, United Kingdom patent specification 1,256,639 to Botting; U.S. Pat. Nos. 2,644,152 to Ginsberg; 2,719,506 to Sequeira. However, everyday environmental conditions can cause the heated filaments in these light sources to fail such as variations in temperature and voltage. Further, incandescent light sources are particularly susceptible to failure from shock or vibration. Thus, any single one or any combination of these environmental conditions can destroy the filament and render the lamp useless. Lamps using the incandescent light bulbs often require constant replacement of the batteries used to power the lamps due to the power requirements of the bulbs.
LED(light emitting diodes) can emit a longer lasting and cheaper light source than an incandescent bulb. However, basic LEDs are not omni-directional. An LED emits up to a 90 degree cone of light. Various techniques such as combining plural LEDs together and using additional diffusion methods on the LEDs themselves have been attempted in order to increase the viewing angle of the LED. See for example, U.S. Pat. Nos. 5,122,781 to Saubolle and 5,140,220 to Hasegawa. However, these techniques add additional manufacturing costs in assembly and materials. Furthermore, these techniques due not create a fully emitting omni-directional light.
Thus, the need exists for an effective omni-directional light source for traffic control and warning lamps that avoids the problems of the prior art previously discussed.